tailieunhanh - Báo cáo khoa học: "A generic model of forest canopy conductance dependent on climate, soil water availability and leaf area index"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: A generic model of forest canopy conductance dependent on climate, soil water availability and leaf area index. | 755 Ann. For. Sci. 57 2000 755-765 INRA EDP Sciences Original article A generic model of forest canopy conductance dependent on climate soil water availability and leaf area index André Graniera Denis Loustaub and Nathalie Brédaa a Institut National de la Recherche Agronomique Unité d Ecophysiologie Forestiere 54280 Champenoux France b Institut National de la Recherche Agronomique Unité de Recherches Forestieres BP 45 33611 Gazinet Cedex France Received 2 June 2000 accepted 3 October 2000 Abstract - This paper analyses the variation in tree canopy conductance for water vapour gc in order to derive a general expression including the effects of solar radiation R vapour pressure deficit D leaf area index LAI and extractable soil water. Canopy conductance was calculated from transpiration measured in 21 broadleaved and coniferous forest stands under different climates temperate mountain tropical and boreal. Common features in the dependence of gc on climate and on soil water content were exhibited. When soil water was not limiting gc was shown to increase linearly with LAI in the range 0 to 6 m2 m-2 and reach a plateau value. Besides the positive effect of increasing R and the negative effect of increasing D on gc it was surprisingly shown that a decrease in extractable soil water induced a similar reduction in gc in various tree species equally in coniferous and in broadleaved. Based on these findings a general canopy conductance function is proposed. canopy conductance sap flow transpiration species comparison leaf area index water stress model synthesis Résumé - Un modèle générique de conductance de couverts forestiers dependant du climat de la disponibilité en eau dans le sol et de l indice foliaire. Ce travail réalise l analyse des facteurs de variation de la conductance du couvert pour la vapeur d eau gc avec l objectif d en donner une expression générale prenant en compte les effets du rayonnement global R du déficit de saturation de l air D de l indice foliaire